The present invention pertains generally to the preparation of glycoside products by the acid catalyzed reaction of an alcohol reactant and a saccharide reactant. More particularly, such invention relates to a process for the preparation of such glycoside products directly from an aqueous solution or syrup of said saccharide reactant without having to first convert said saccharide reactant to substantially dry anhydrous or crystalline form.
Alkyl glycoside products such as, for example methyl glycoside, ethyl glycoside, propyl glycoside, butyl glycoside, etc. and their alkyl polyglycoside counterparts are generally known as is the preparation thereof via the reaction of an alcohol reactant and a saccharide reactant in the presence of a suitable acidic catalyst. See in this regard U.S. Pat. No. 2,390,507 to Cantor (issued Dec. 11, 1945); U.S. Pat. No. 3,219,656 to Boettner (issued Nov. 23, 1965); U.S. Pat. No. 3,450,690 to Gibbons et al. (issued June 17, 1969) and U.S. Pat. No. 3,974,138 to Lew (issued Aug. 10, 1976).
Also known is the fact that lower alkyl glycosides such as methyl, ethyl, propyl, butyl, etc. glucosides are useful as intermediates for the preparation of longer chain (e.g., higher alkyl) glycoside products which in turn have surface active characteristics and are useful in a variety of surfactant, emulsifier, detergent, etc. end-use applications.
In the manufacture of water soluble alkyl glycoside products from water-soluble monosaccharide and polysaccharide starting materials (such as glucose, maltose, sucrose, xylose, lactose, and the like) by the acid catalyzed reaction thereof with an alcohol reactant (such as, for example, propanol, butanol, amyl alcohol, 2-ethylhexyl alcohol, octyl alcohol, etc.), it has generally been the practice to introduce the saccharide reactant into the reaction mixture in substantially dry (e.g., anhydrous or hydrated crystalline) form and to conduct said reaction under substantially anhydrous conditions so as to avoid the formation of substantial quantities of undesired insoluble higher polysaccharide reaction by-products.
Crystalline dextrose is relatively expensive as a potential starting point saccharide raw material. Similarly, the inclusion of a special step in the overall reaction process for the preliminary conversion of an aqueous saccharide solution or syrup feed stream into substantially dry, anhydrous or crystalline form prior to the use thereof in the desired saccharide/alcohol reaction entails or introduces added complication and expense to the overall glycoside manufacturing process. Accordingly, it would be highly desirable to provide a process whereby an aqueous saccharide solution or syrup could be directly reacted with an alcohol reactant (i.e. without the special need for conducting said reaction under substantially anhydrous conditions) while at the same time avoiding the generation of substantial quantities of undesired insoluble higher polysaccharide by-product materials.